Rheem PROG50-42N RH67 PV Professional Classic Residential 42K BTU Power Vent Natural Gas Water Heater, 50-Gallon Uses indoor air for combustion; blower exhausts the flue gases Exclusive air/fuel shut-off device. Maintenance free - no filter to clean Long venting lengths up to 100 equivalent feet Rheum exclusive R-Tech (registered) anode rod provides long-lasting tank protection This new Model number replaces the old Model number 43VP50E2